Telephone system.



W W, BEAN. TELEPHONE SYSTEM;

MPLIOATION FILED Dgo. 23, 1902,

UNTTED STATES PATENT ernten.

WILLIAM WV. DEAN, .OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG SWITCHBOARD AND SUPPLY COMPANY, .O F CHICAGO, ILLINOIS, A

CORPORATION OF ILLINOIS.

TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented oct. 2, 1906.' A

Application filed December 23, 1902. Serial No. 136,332.

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Be it known that I, WILLIAM W. DEAN, a citizen of the United States ofAmerica, residing at Chicago, in the county of Cook and State ofIllinois, have invented new and useful Improvements in TelephoneSystems, of which the following is a specification.

My invention relates to improvements in telephone systems whereby thelines which are of the common-battery multiple-switchboard type areprovided with only a single relay or electromagnetic signaling device.The apparatus for a telephone-line usually requires a line-relay tooperate the line-signal and a cut-ofi relay actuated during a connectionfor conversation to rendersaid relay or signal inoperative. In myinvention I provide a single device which is capable of performing allthe functions of the two devices of the ordinary line.

My invention is shown in the accompanying drawing, which representsdiagrammatically a telephone system embodying my improvements and inwhich the same reference characters are used throughout to designatesimilar parts.

The subscribers lines L and L2 extend from their respective substationsA and C to the central ofiice, where they are fitted with the usualspring-jacks or connection-terminals, such as J, J2, and J3, in anydesired number and with a line-signal S, which is preferably in the formof a small incandescent lamp having its circuit controlled through thenormally open contacts of the relay R. The line conducton2 includes a hihresistance winding 4 ofthe relay R an is then connected by conductor 5with the live pole of a battery B, preferably common to the exchange orto a large number of lines thereof. A line conductor 3 includes thehelix 6 of low resistance of said relay R and is thence connected toground or the common office return. These windings or helices 4 and 6are differentially disposed on the core of the magnet with reference tosteady currents in the metallic line and arc preferably wound end on toprevent the passage' therethrough of the voice-currents. At thesubstation of the line any suitable common-battery outfit maybe employedand which is die, agrammatically indicated in the drawing.

This spcial apparatus includes a transmitter '7 vand receiver 8 in abridge of the lineconductors, which is normally open at the switch-hook9, while'an ordinary call-bell 10 and condenser 11 are connected,preferably, in'a permanent bridge 'of the line conductors. Both lines,and, in fact, all lines of the exchange, are ofv the same type, andhence the description ofone sufIices for al1.

The operators cord circuit, of which there may be as many as desired7comprises a pair of plugs P and P2, each having tip and sleeve contactsadapted to register with the like contact-surfaces of. the spring-jacksor connection-terminals of the lines and the tipcontacts of which plugsare joined together by the strands t and t2 and the interposed condenserc, while the sleeve-contacts thereof are inductively joined by thesimilar fleXi-iLL ble strands s and s? and the condenser c2. At theanswering end of the cord-circuit a air of supervisory relays r and r2are bri ged across, and an intermediate point of the bridge is joined bya suitable conductor, such as 12, with the live pole of said'battery B.The tip-relay is preferably of one hundred ohms resistanceand thesleeve-relay of about iive hundred ohms. These relays control thecircuit of the supervisory lamp S2, which is normally closed at thecontacts of relay r and normally opened at the contacts of relay r2. Asimilar set of relays r3 and r4 are connected across the calling end ofthe cord-circuit, an intermediate point of which connection joined byconductor 13 with the live poleof said battery B. These relays similarlycontrol the local circuit of the supervisory lamp S3, associated withthe calling end of the cord-circuit.

For testing purposes the tip-strand t2 of the cord-circuit is severed atthe spring 14 of sleeve relay r, which normally connects, Ithroughconductor 15, with the high-resistance and high -impedance test relay1'5, which is grounded upon its other terminal. The operatorstransmitter 16 is connected together with a retardation-coil 17 in aconductor 13, leading to the common wire 5a, which is joined to the livepole of the battery B. The said transmitter is shunted by the primaryhelix of the operators inductioncoil 19 and by a suitablecondenser c3.The

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' bridge of the calling end of the cord-circuit to thereby ring thesubscriber's bell.

The subscriber A desiring a connection takes up' his receiver', andthereby closes a path for current from the battery B through thedifferential windings of the relay R, which, owing to the difference inresistance of the two relays, is unbalanced and attracts its armature toclose a local circuit of the line-signal. rThe operation of the signalat-A tracts the operators attention, whereupon the answering-plug P ofher cord-circuit is inserted ink the answering-jack of the line. Thisact places the supervisory relay fr in shunt of the high-resistancewinding 4 of the relay R and the supervisory relay r2 in series with thelowresistance helix 6 of the said relay R. These relays and windings areso proportioned that under these conditions the magnetic effects of thecurrent flowing through the two windings 4 and 6 of the re lay R areequal and opposite, thus neutralizing the said relay and causing itsarmature to fall away and open the circuit of the lamp S to extinguishit.

Upon learning the number of the party wanted the line is tested in theusual way by touching the tip of the calling-plug to the test-ring ofthe multiple-jack before the operator. When the line is busy, thetest-rings are raised to the potential of -the battery B and a flow ofcurrent results through the testrelay T5, which responds and closes thecir-A cuit for current through the primary helix of the operatorsinduction-coil, and thereby causes a click in her receiver'. lf the lineis idle, however, the test-rings are at the same potential as the tip ofthe plug, and consequently no fiow of current results and 'no click isreceived, Upon finding the line idle, the calling-plug P2 is inserted inone of the multiple-jacks of the line and the ringing-l ey depressed tocall the wanted subscriber. The relay R of the called line does notrespond to the ringing-current, so that the line-signal of that lineremains unexposed and only the subscribers bell is operated. Afterringing the subscriber and before his response current liows through thesleevestrand of the cord-circuit operating the sleeve supervisory relayr4; but the relay R is so adjusted that the current through the winding6 is not now sufficient to operate the same, and therefore theline-signal of the line called does not respond. The supervisory lamp S3is now lighted toindicate the failure of the calledsubscriber torespond. rl`he tip-strand` t2 is closed for talking purposes throughspring 14 and its forward contact of the relay r4. Uponthe response ofthe called subscriber current flows over the metallic line and operatesthe supervisory relay rf to open the circuit of and extinguish the lampS3.

During conversation the battery B furnishes current through thesupervisory relays r and yr and over the telephone-lines fortransmission purposes, the return-path for current being through thelow-resistance winding 6 of the relay R. The line resistance is shuntedby that ofthe sleeve supervisory relay or r4; but with an average line asufficient margin is obtained for satisfactory operation.

At the termination of the conversation the return of the receivers tothe hooks opens the line-circuits, thereby deenergizing the tipsupervisory relays and permitting the supervisory-lamp circuits tobeclosed. Uponobserving these signals the operator takes down theconnection and restores all parts to normal condition. It will beunderstood that the relays 12 and 1f* remain energized when theline-circuits are open by current through the local path, including saidrelays and the winding 6 of the line-relay, the latter, as beforeexplained, being adjusted so as not to respond to this current.

While the resistances mentioned are notI intended to be arbitrary, goodresults have been secured., as before explained, when the supervisoryrelays are 100 and 500 ohms re-v sistance and the windings of the relayR of 100 and 500 ohms, respectively. Under these conditions a sufficientmargin is obtained when the total line resistance varies between 0 and1300ohms,the other apparatus being of the usual or desired dimensions.rl`he grounds mentioned may be one and the saine or the common ofiicereturn, and the substation apparatus maybe of anydesired common-batterytype.

I claimi l. In a telephone system, the combination with atelephone-line, ofan electromagnetic line signaling device havingdifferentiallydisposed windings and of different magnetic effects whencalling-current from the substation flows through said windings, andmeans for equalizing the magnetic effects of said windings' when aconnection is established with the line to render the same inop erative,substantially as described.

2. In a telephone system, the combination with a telephone-line, of anelectromagnetic line signaling device therefor having differentialwindings capable of developing different strengths of magnetic fieldwhen traversed by current in series, and means for equalizing themagnetic effects of said wind IIO ings when a connection is establishedwith the line, substantially as described.

3. In a telephone system, the combination with a tele'ihone-line, of aline signaling device having two windings capable of producing dil'erentmagnetic eli'ects when traversed by the same current, a common source ofcurrent at the central oliice, means to operate said device by causingthe same current to traverse said two windings in series, and means torender said device inoperative by causing a different current totraverse the two wind ings, substantially as described,

4. In a telephone system, the combination with a line signaling devicehaving two diilerential windings disposed in the path ol cur-'l' rontwhen the subscriber is calling the central o'lllce, said windings beingadapted to produce different magnetic effects" as said current passestherethrough, and means for rendering said device inoperative whenconnection is established with the line, substaiitially as described. i

5. In a telephone system, the combination with a telephone-line, of aline-relay therefor having two differential windings serially disposedin the path of current when the subscriber is calling the central olliceand responsive thereto, and means for rendering the same inoperativewhen a connection is established with the line, substantially asdescribed.

6. In a telephone system, the combination with a telephone-line, ofa/-line signaling device therefor having' unequal di'li'erentialwindings disposed serially in the path of current when the subscriber iscalling the central o'tlice, 'said device being responsive to suchcurrent, and means for rendering said device inoperative when aconnection is established with the line, substantially as described. i

7. In a telephone system, the combination with a telephone-line, of alinevsignaling device therefor having two dil'erential windings, ineansfor causing a current to iiow through both said windings so as toproduce a magnetic field in each and operate the same when a subscriberis calling central oilice, and means for causing current to flow throughsaid windings so as to neutralize each other and render the sameinoperative when a connection is establishedwith the line, substantially as described.

8. In a telephone system, the combination with a telephone-line, ofa-line signaling device therefor having two unequal windingsdifferentially' disposed with reference to current in the line when thesubscriber is calling the central oilce?, said device responding to suchcurrent and means for causing current through said windingsto produceequal and opposite 'effects when a connection is established with theline, wherebythe same is rendered inoperative, substantially asdescribed.

9. In a telephone system, the combination with a telephone-line, of aline signaling device therefor having two unequal windingsdifferentially disposed with reference to current in the line when thesubscriber is calling the central ollice, whereby the same responds tosuch calling-current, a-cord-circuit to establish conversationalcircuits with the line, supervisory apparatus associated therewith, andmeans whereby when a connection is established. by the cord-circuit withthe line, the magnetic effects of the two windings of the said deviceare neutralized and the supervisory apparatus is suitably actuated,substantially as described.

l0. In a telephone system, the combination with a telephone-line, of aline signaling device having two windings, a cord-circuit to establishconnections 'with the line, supervisory apparatus associated therewithincluding a pair of electromagnetic windings, means for connecting oneof said windings in parallel with one of the windings of said device inthe line-circuit, and means for connecting the other electromagneticwinding in a local circuit in series with the other winding of saiddevice, substantially as described.

11. In a telephone system, the combination with a telephone-line, of aline signaling device having a high-resistance and a lowresistancewinding, a cord-circuit to establish connections with the line, asupervisory apparatus, having a high-resistance and a loweresistanceelectromagnetic winding associated therewith, and means when thecordcircuit is connected with the line to connect said low-resistancesupervisory winding in shunt of the high-resistance winding of saiddevice and the high-resistance supervisqry device in series with thelow-resistance wi1iding of the line signaling device, substantially asdescribed.

12."In a telephone system, the combination with a telephone-line, of aline signaling device therefor, an electromagnet having windings thereoncapable of producing dif ferent magnetic effects when traversed by thesame current,'a central battery, means to operate said magnet by currentfrom said battery when a subscriber is calling the central oilice, andmeans to render said magnet inoperative when a connection is establishedwith the line for conversation, said means being adapted to vary thecurrent relation in said coils, substantially as described.

13. In a telephone system, the Acombination with a telephone-line, of aline signaling device having a high-'resistancewinding and alow-resistance winding, one in each side of the line-circuit, acord-circuit having a pair of supervisory relays associated therewith,

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one of low resistance and the other of high resistance, a source of.current associated with said relays and means for connecting thelow-resistance relay iii parallel with the lsaid high-resistance windingwhen a connection is established with said line, and ahighresistancerelay in shunt with the line resistance and in series with saidlow-resistance winding, substantially as described.

14. n a telephone system, the combination with a telephoneline, 40i amagnetic line signaling device therefor, two windings for said device,means yto energize the device when equal current flows through saidwindin s and to denergize' the device by causing di erent currents toHow through the two windings, substantially as described.

l15. In a telephone system, the combination with a telephone-line, of aline signaling device having a high-resistance winding and alow-resistance winding, one in each side of the line-circuit, acord-circuit having apair of supervisory relays associated therewith,one of low resistance and thel other of high resistance, a source ofcurrent associated with said relays and havingone pole connecteddirectly thereto, and means for con` necting the loweresistance relay inparallel with the said high-resistance winding when a connectionisestablished with said line, and the high-resistance relay in shunt withthe line resistance and in series with said lowresistancewinding,substantially as described.

Signed by ine at Chicago, county of Cook, State of Illinois, this 15thday of December,

WILLIAM W. DEAN.

Witnesses:

ROBERT LEWIS AMES,

GAZELLE BEBER.

